Preparation of alkoxylation products in the presence of mixed hydroxides modified with additives

ABSTRACT

Alkoxylation products are prepared by reacting compounds having active hydrogen atoms with C 2  -C 4  -alkylene oxides in the presence of a mixed hydroxide built up of polycations and modified with additives and having the general formula I or II 
     
          M(II).sub.1-x M(III).sub.x (OH).sub.2 !A.sub.x/n ·m L(I) 
    
     
          LiAl.sub.2 (OH).sub.6 !A.sub.1/n ·m L            (II) 
    
     where 
     M(II) is at least one divalent metal ion, 
     M(III) is at least one trivalent metal ion, 
     A is at least one inorganic anion and 
     L is an organic solvent or water, 
     n is the valence of the inorganic anion A or in the case of a plurality of anions A is their mean valence and 
     x can assume a value of from 0.1 to 0.5 and 
     m can assume a value of from 0 to 10, 
     as alkoxylation catalyst, wherein the mixed hydroxide contains additives.

This is the U.S. National Stage Application of PCT/EP/94/02195 filedJul. 5, 1994 now WO95/04024 published Feb. 9, 1995.

The present invention relates to an improved process for preparingalkoxylation products by reacting compounds having active hydrogen atomswith C₂ -C₄ -alkylene oxides in the presence of a mixed hydroxide builtup of polycations and modified with certain additives as alkoxylationcatalyst. Since some of these mixed hydroxides are new compounds, theinvention further relates to these new mixed hydroxides and processesfor their preparation.

Alkoxylation products having a narrow molecular weight distribution orhomologue distribution, known as "narrow cut", "narrow range" or"peaked" alkoxylates, are becoming increasingly important since theyhave improved use properties in comparison with normal alkoxylateshaving a broad distribution, and are conventionally prepared usingalkali metal hydroxides or boron trifluoride adducts as catalysts. Theyare mainly used as surfactants in detergents, cleaning compositions andpersonal care compositions, but also in the paper and textile fibersindustry. Efficient synthetic routes to such narrow cut alkoxylates aretherefore urgently sought.

DE-A 40 10 606 (1) relates to the use of hydrotalcites hydrophobicizedwith anions of an aliphatic C₄ -C₄₄ -dicarboxylic acid or an aliphaticC₂ -C₃₄ -monocarboxylic acid as ethoxylation or propoxylation catalystsfor compounds having active hydrogen atoms or for fatty acid esters. Thealkoxylation products obtained using these catalysts have a narrowhomologue distribution.

DE-A 40 34 305 (2) discloses double-layer hydroxide compounds containingmagnesium, zinc, calcium, iron, cobalt, copper, cadmium, nickel ormanganese as divalent metal and aluminum, iron, chromium, manganese,bismuth or cerium as trivalent metal and carbonate, hydrogencarbonate,sulfate, nitrate, nitrite, phosphate, hydroxide or halide as inorganicanion in addition to hydroxide and hydrophobicized with anions of analiphatic C₄ -C₄₄ -dicarboxylic acid or an aliphatic C₂ -C₃₄-monocarboxylic acid. These compounds are recommended as alkoxylationcatalysts for compounds having active hydrogen atoms or fatty acidesters.

WO-A 92/11224 (3) relates to an alkoxylation process for alcohols togive glycol ethers using an anionic double-hydroxide clay such ashydrotalcite having an essentially intact layer structure asalkoxylation catalyst, which clay contains anions of the alcohol beingreacted built in between the layers. Alcohols specified for this purposeare aliphatic, cycloaliphatic or aromatic alcohols, preferably having upto 8 carbon atoms, eg. methanol, ethanol, cyclohexanol or phenol.

However, the specified alkoxylation catalysts still have a series ofdeficiencies. In particular, the content of polyalkylene glycol formedas by-product in the alkoxylation and of unalkoxylated starting compoundare still too high. The molecular weight distribution is likewise stilltoo broad.

It is an object of the present invention to provide alkoxylationcatalysts which can be prepared more efficiently and at the same timesimply and economically and which no longer have the abovementioneddeficiencies.

We have found that this object is achieved by a process for preparingalkoxylation products by reacting compounds having active hydrogen atomswith C₂ -C₄ -alkylene oxides in the presence of a mixed hydroxide builtup of polycations and modified with additives and having the generalformula I or II

     M(II).sub.1-x M(III).sub.x (OH).sub.2 !A.sub.x/n ·m L(I)

     LiAl.sub.2 (OH).sub.6 !A.sub.1/n ·m L            (II)

where

M(II) is at least one divalent metal ion,

M(III)is at least one trivalent metal ion,

A is at least one inorganic anion and

L is an organic solvent or water,

n is the valence of the inorganic anion A or in the case of a pluralityof anions A is their mean valence and

x can assume a value of from 0.1 to 0.5 and

m can assume a value of from 0 to 10,

as alkoxylation catalyst, wherein the mixed hydroxide contains asadditives

(a) aromatic or heteroaromatic mono- or polycarboxylic acids or theirsalts,

(b) aliphatic mono- or polycarboxylic acids or their salts having anisocyclic or heterocyclic ring in the side chain,

(c) monoesters of dicarboxylic acids or their salts,

(d) carboxylic anhydrides,

(e) aliphatic or aromatic sulfonic acids or their salts,

(f) C₈ -C₁₈ -alkyl sulfates,

(g) long-chain paraffins,

(h) polyetherols or polyether polyols or

(j) alcohols or phenols, which are not built in between the layers ofthe mixed hydroxide I or II.

Suitable divalent metal ions M(II) are, in particular, zinc, calcium,strontium, barium, iron, cobalt, nickel, cadmium, manganese, copper andespecially magnesium.

Suitable trivalent metal ions M(III) are, in particular, iron, chromium,manganese, bismuth, cerium and especially aluminum.

Suitable inorganic anions A are, in particular, hydrogencarbonate,sulfate, nitrate, nitrite, phosphate, chloride, bromide, fluoride,hydroxide and especially carbonate.

The valence or the mean valence n of the inorganic anion(s) A isnormally in the range from 1 to 3.

L is an organic solvent, in particular an alcohol such as methanol,ethanol or isopropanol, or especially water.

A large number of mixed hydroxides comprising divalent and trivalentmetals and built up of polycations is known. Also known are such mixedhydroxides comprising monovalent and trivalent metals ("lithiumaluminates", see general formula II). The majority of these compoundshas a layer structure (typical representative: hydrotalcite), but mixedhydroxides having a different structure are also known.

For mixed hydroxides having a layer structure, the literature gives anumber of synonymous names, eg. "Anionische Tone", "Anionic clays","Hydrotalkit-ahnliche Verbindungen", "Layered double hydroxides(=LDHs)", "Feitknechtverbindungen" or "Doppelschichtstrukturen".

The class of mixed hydroxides having a layer structure iscomprehensively described in the review articles by Cavani et al. orAllmann (F. Cavani, F. Trifiro and A. Vaccari, "Hydrotalcite-typeanionic clays: preparation, properties and applications", CatalysisToday, 11 (1991) 173-301; R. Allmann, "Doppelschichtstrukturen mitbrucitahnlichen Schichtionen", Chimia 24 (1970) 99-108).

Examples of mixed hydroxides built up of polycations and not having alayer structure are the ettringites. These compounds were described byFeitknecht et al., their structure was determined by Moore et al. (W.Feitknecht und H.W. Buser, "Zur Kenntnis der nadeligenCalcium-Aluminumhydroxysalze", Helv. Chim. Acta 32 (1949) 2298-2305; A.E. Moore und H. F. Taylor, "Crystal structure of ettringite", ActaCryst. B 26 (1970) 386-393).

Characteristic of all mixed hydroxides used according to the presentinvention is a structure comprising positively charged mixed hydroxideunits (polycations) between which anions are located to balance thecharge. In addition to the anions A, solvent molecules L are generallyalso located between the positively charged units. These polycations aregenerally layers, but can also, eg. in the case of ettringite, assumeother shapes. The anions between the polycations can generally beexchanged.

The structure of the mixed hydroxides, particularly the distance of thepolycations from one another, can be determined by X-ray diffraction.The distances of the polycations from one another, eg. the layerspacings in hydrotalcite, depend mainly on the nature of the anions Aand can be from about 4 Å to about 45 Å.

An important representative of mixed hydroxides having a layer structureis hydrotalcite. Naturally occurring hydrotalcite has the chemicalcomposition Mg₆ Al₂ (OH)₁₆ !CO₃ ·4H₂ O. Hydrotalcite has a structure inwhich brucite-like layers carry a positive charge owing to thereplacement of some divalent magnesium ions by trivalent aluminum ions.These polycation layers alternate with intermediate layers containingcarbonate anions and water. The structure of hydrotalcite iscomprehensively described in the above-cited literature, eg. by Cavaniet al.

Simple hydroxide salts which are built up of polycations and anionslocated in between are also known. While the above-described mixedhydroxides are built up of heteropolycations, this structure of suchcompounds comprises isopolycations. An example is hydrozincite (basiczinc carbonate) whose structure has been determined by Ghose (S. Ghose,"The crystal structure of hydrozincite, Zn₅ (OH)₆ (CO₃)₂ " Acta Cryst.17 (1964) 1051-1057). Compounds of this class can likewise serve asstarting materials for alkoxylation catalysts.

On heating the mixed hydroxides, the solvent located between thepolycations, usually water of crystallization, is first given off at upto about 200° C. At higher temperatures, for instance on calcination at500° C., the polycations are degraded with destruction of the structureand the anion may also be decomposed. The calcination is, if not carriedout at excessively high temperatures, reversible (known as the "memoryeffect").

Mixed hydroxides can be prepared relatively simply in the laboratory. Inaddition, a number of these compounds occur naturally as minerals;examples of these are:

Hydrotalcite Mg₆ Al₂ (OH)₁₆ !CO₃ ·4H₂ O

Tacovite Ni₆ Al₂ (OH)₆ !CO₃ ·4H₂ O

Hydrocalumite Ca₂ Al(OH)₆ !OH·6H₂ O

Magaldrate Mg₁₀ Al₅ (OH)₃₁ !(SO₄)₂ ·mH₂ O

Pyroaurite Mg₆ Fe₂ (OH)₁₆ !CO₃ ·4.5H₂ O

Ettringite Ca₆ Al₂ (OH)₁₂ !(SO₄)₃ ·26H₂ O

The synthesis of a mixed hydroxide in the laboratory is generallycarried out by precipitation, with a solution containing the cations indissolved form is combined with a second alkaline solution containingthe anion(s) in dissolved form. The exact way in which thisprecipitation is carried out (pH, temperature, ageing of theprecipitate) can have an influence on the chemical composition of theprecipitated compound and/or its crystallite morphology.

For the alkoxylation process of the present invention, preference isgiven to those mixed hydroxides of the general formula I in which M(II)is magnesium, M(III) is aluminum and A is carbonate. Particularlysuitable is naturally occurring or synthetically prepared hydrotalcite.

The following classes of substances are suitable for the modificationaccording to the present invention ("hydrophobicization") of the mixedhydroxides described:

(a) aromatic or heteroaromatic mono -or polycarboxylic acids, inparticular mono- or dicarboxylic acids, or their salts, especiallybenzenemonocarboxylic or benzenedicarboxylic acids in which the benzenering can be additionally substituted by one to three C₁ -C₄ -alkylgroups, eg. benzoic acid, p-, m- or p-methylbenzoic acid,p-tert-butylbenzoic acid, p-iso-propylbenzoic acid, p-ethylbenzoic acid,phthalic acid, isophthalic acid, terephthalic acid,pyridinemonocarboxylic and pyridinedicarboxylic acids and also thesodium, potassium and ammonium salts of these;

(b) aliphatic mono-or polycarboxylic acids, in particular mono- ordicarboxylic acids, or their salts having an isocyclic or heterocyclicring in the side chain, eg. phenyl-C₂ -C₄ -alkanoic acids such asphenylacetic acid, 3-phenylpropionic acid or 4-phenylbuteric acid,cyclopentanecarboxylic acid, cyclohexyl-C₂ -C₄ -alkanoic acids such ascyclohexylacetic acid, 3-(cyclohexyl)propionic acid or4-(cyclohexyl)buteric acid, cinnamic acid, o- or p-chlorocinnamic acid,pyridylacetic acids and the sodium, potassium and ammonium salts ofthese;

(c) monoesters of aliphatic and aromatic dicarboxylic acids and theirsalts, preferably C₁ -C₁₈ -alkyl monoesters of phthalic acid,hexahydrophthalic acid, maleic acid or terephthalic acid, eg.monomethyl, monoethyl or monobutyl esters of phthalic acid orterephthalic acid;

(d) aliphatic and especially alicyclic and aromatic carboxylicanhydrides, eg. maleic anhydride, phthalic anhydride orhexahydrophthalic anhydride;

(e) aliphatic or aromatic sulfonic acids and their salts, eg.methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid,p-dodecylbenzenesulfonic acid, naphthalenesulfonic acids,naphtholsulfonic acids and the sodium, potassium and ammonium salts ofthese;

(f) C₈ -C₁₈ -alkyl sulfates, in particular alkali metal C₈ -C₁₈ -alkylsulfates, eg. sodium or potassium decyl sulfate or sodium or potassiumdodecyl sulfate;

(g) long-chain paraffins, in particular C₈ -C₅₀ -n-alkanes, especiallyC₁₀ -C₃₀ -n-alkanes such as n-decan or n-dodecane;

(h) polyetherols or polyether polyols, ie. monohydric alcohols havingether-oxygen bridges (polyetherols, polyalkylene glycol monoethers oresters) or polyhydric alcohols having ether-oxygen bridges (polyetherpolyols), in particular alkoxylated C₁ -C₃₀ -alcohols, alkoxylated C₁-C₃₀ -carboxylic acids of aliphatic or aromatic structure or alkoxylatedC₆ -C₃₀ -phenols, where from 1 to 50 mol, especially from 2 to 30 mol,of a C₂ -C₄ -alkylene oxide or a mixture thereof which in thealkoxylated product leads to a random mixture or preferably a blockingof the various alkylene oxide units are used per mole of hydroxyl group;some of the additives (h) are structurally identical with the productsobtained in the alkoxylation according to the present invention ofcompounds having active hydrogen atoms using the correspondinglyadditive-treated mixed hydroxides I or II;

(j) alcohols or phenols, which are not built in between the layers ofthe mixed hydroxide I or II (if this mixed hydroxide has a layerstructure), in particular aliphatic or cycloaliphatic C₁ -C₃₀ -alcoholsor C₆ -C₃₀ -phenols, especially n-alkanols (fatty alcohols) having from9 to 18 carbon atoms, eg. n-decanol, n-dodecanol, n-tetradecanol,n-hexadecanol or n-octadecanol; some of the additives (j) arestructurally identical with the compounds having active hydrogen atoms,such as the compounds III, used as starting materials in thealkoxylation of the present invention using the correspondinglyadditive-treated mixed hydroxides I or II.

It is also possible to use mixtures of said additives from one of theclasses (a) to (j) or from different classes.

The monoesters (c) can be advantageously obtained by reacting thecorresponding carboxylic anhydrides, for example the anhydrides (d),with alcohols such as C₁ -C₁₈ -alkanols. It is also possible to usemixtures as alcohol component. Suitable anhydride components are, forexample, phthalic anhydride, hexahydrophthalic anhydride or maleicanhydride. It is here also possible to use the alcohol component inexcess, so that it simultaneously serves as solvent in the modificationof the mixed hydroxides. If an alcohol serves as hydrogen-activecompound in the alkoxylation, it is best to select this alcohol for thereaction with anhydrides, so that complicated filtration and drying canbe omitted.

In a preferred embodiment, the alkoxylation process of the presentinvention makes use of a mixed hydroxide I or II containing as additivesbenzenemonocarboxylic or benzenedicarboxylic acids in which the benzenering can be additionally substituted by from one to three C₁ -C₄ -alkylgroups, phenyl-C₂ -C₄ -alkanoic acids, cyclohexanecarboxylic acid,cyclohexyl-C₂ -C₄ -alkanoic acids, C₁ -C₁₈ -alkyl monoesters of phthalicacid, hexahydrophthalic acid, maleic acid or terephthalic acid, maleicanhydride, phthalic anhydride, hexahydrophthalic anhydride,benzenesulfonic acid, p-toluenesulfonic acid, p-dodecylbenzenesulfonicacid, alkali metal dodecyl sulfates, n-dodecane, n-alkanols having from9 to 18 carbon atoms or salts of the acids specified.

Very particularly preferred additives are benzoic acid and its alkalimetal salts because of the excellent properties as alkoxylationcatalysts and the good economics of these compounds, ie. their ready andinexpensive availability.

The molar ratio of the additives (a) to (j) to the mixed hydroxides I orII is usually from 0.01:1 to 10:1, especially from 0.05:1 to 5:1, inparticular from 0.2:1 to 2:1.

The structure of the mixed hydroxides is essentially retained after themodification with the additives (a) to (j); in particular, thepolycations remain essentially unchanged. The distances of thepolycations from one another can be changed to a greater or lesserextent in the modification. In some cases, the additives are presentafter the modification in neutral or anionic form between thepolycations of the mixed hydroxides, with them being able to completelyor partially displace the anions located there. In certain cases, themodification of the mixed hydroxides can also be regarded as a type ofreplacement of the anions originally present by additive anions oranions formed from the additive. The intercalation of the additivesbetween the polycations of the mixed hydroxides generally becomesevident in an increase in the distance between the polycations and canbe confirmed by X-ray diffraction.

Such a modification can be carried out for the purposes ofhydrophobicization, changing the dispersibility, changing the catalyticproperties and/or changing the theological properties of the mixedhydroxides. In other cases, the modification results merely in a coatingof the surface of the mixed hydroxides, with the spacing of thepolycations remaining unchanged. Such a surface coating can, forexample, also serve to hydrophobicize the mixed hydroxides.

Compounds having active hydrogen atoms which can be used are allcompounds which have one or more acid hydrogen atoms which can reactwith alkylene oxides. Particular mention may here be made of alcohols,phenols, carbohydrates, carboxylic acids, carboxamides, amines andmercaptans which are represented by the general formula III ##STR1##where R is a usual hydrocarbon radical which can also contain heretoatoms and bear further functional groups, Y is O, S, NH or NR and k is1, 2 or 3.

Depending on the value of k, the radicals R can be monovalent, divalentor trivalent. Preference is given to monovalent and divalent radicals,the most important are monovalent radicals.

Radicals R deserving special mention are:

straight-chain or branched C₁ -C₃₀ -alkyl groups and C₃ -C₃₀ -alkenylgroups which can be interrupted by one or more non-adjacent oxygen atomsand can bear additional hydroxyl groups, eg. methyl, ethyl, n-propyl,iso-propyl, n-butyl, 2-ethylhexyl, n-octyl, iso-nonyl, n-decyl,n-dodecyl, iso-tridecyl, myristyl, cetyl, stearyl, eicosyl, 2-propenyl,oleyl, linoleyl, linolenyl, 2-methoxyethyl, 2-ethoxyethyl,2-butoxyethyl, 4-methoxybutyl, 4-(4'-methoxybutyloxy)butyl,2-hydroxyethyl or 4-hydroxybutyl;

C₁ -C₃₀ -acyl groups which can additionally bear hydroxyl groups, eg.formyl, acetyl, propionyl, butyryl, valeryl, decanoyl, lauroyl,myristoyl, palmitoyl, stearoyl or lactyl;

monovalent carbohydrate radicals of monosaccharides or disaccharideswhen Y=O, eg. radicals of glucose, mannose, fructose, sucrose, lactoseor maltose;

aryl groups having a total of from 6 to 20 carbon atoms, which can beadditionally substituted by C₁ -C₄ -alkyl groups, hydroxyl groups, C₁-C₄ -alkoxy groups and amino groups, eg. phenyl, tolyl, xylyl,hydroxyphenyl, methoxyphenyl, aminophenyl or naphthyl;

arylcarbonyl groups having a total of from 7 to 21 carbon atoms, whichcan be additionally substituted by C₁ -C₄ -alkyl groups, hydroxylgroups, C₁ -C₄ -alkoxy groups and amino groups, eg. benzoyl;

divalent radicals derived, for example when Y=O, from diols,dihydroxyaromatics or bisphenols, such as 1,2-ethylene, 1,3-propylene,1,4-butylene, phenylene or the radical of bisphenol A;

trivalent radicals derived, for example when Y=O, from triols such asglycerol;

polyvalent radicals derived, in particular, from polyols (Y=O), eg.pentaerythritol, or from carbohydrates.

In a preferred embodiment, the hydrogen-active compounds III used are C₁-C₃₀ -alkanols and C₃ -C₃₀ -alkenols, in particular C₈ -C₃₀ -alkanolsand C₈ -C₃₀ -alkenols (fatty alcohols).

Suitable C₂ -C₄ -alkylene oxides are especially 1,2-propylene oxide,1,2-butylene oxide, 2,3-butylene oxide and in particular ethylene oxide.

The modified mixed hydroxides described are generally used in thealkoxylation reactions in amounts of from 0.1 to 5% by weight,preferably from 0.15 to 2% by weight, particularly preferably from 0.2to 0.8% by weight, based on the weight of the compounds having activehydrogen atoms.

The alkoxylation reactions are usually carried out at from 80° to 230°C., preferably at from 100° to 200° C., particularly preferably at from160° to 180° C. The reaction is generally carried out under pressure,for example in an autoclave at from 2 to 10 bar, in particular from 3 to7 bar. The reaction is advantageously carried out without solvent, butan inert solvent can be added.

Some of the mixed hydroxides I and II are new compounds. The presentinvention therefore also provides mixed hydroxides built up ofpolycations and having the general formula Ia or IIa

     M(II).sub.1-x M(III).sub.x (OH).sub.2 !A.sub.x/n ·m L(Ia)

     LiAl.sub.2 (OH).sub.6 !A.sub.1/n ·m L            (IIa)

where

M(II) is at least one divalent metal ion,

M(III) is at least one trivalent metal ion,

A is at least one inorganic anion and

L is an organic solvent or water,

n is the valence of the inorganic anion A or in the case of a pluralityof anions A is their mean valence and

x can assume a value of from 0.1 to 0.5 and

m can assume a value of from 0 to 10,

which have been modified with

(a) aromatic or heteroaromatic mono- or polycarboxylic acids or theirsalts,

(b) aliphatic mono- or polycarboxylic acids or their salts having anisocyclic or heterocyclic ring in the side chain,

(c) monoesters of dicarboxylic acids or their salts,

(d) carboxylic anhydrides,

(e) aliphatic or aromatic sulfonic acids or their salts,

(f) C₈ -C₁₈ -alkyl sulfates,

(g) long-chain paraffins,

(h) polyetherols or polyether polyols or

(j) alcohols or phenols, which are not built in between the layers ofthe mixed hydroxide Ia or IIa,

as additives,

with the exception of benzoic acid and its salts in the case of alithium-aluminum mixed hydroxide having a layer structure,

with the exception of terephthalic acid, p-toluenesulfonic acid,2-naphthol-6-sulfonic acid, p- and o-chlorocinnamic acid and thecorresponding salts and of n-dodecyl sulfate in the case ofmagnesium-aluminum mixed hydroxides having a layer structure,

and also with the exception of phthalic acid, isophthalic acid,terephthalic acid and pyridinedicarboxylic acids in the case ofcalcium-aluminum mixed hydroxides.

The literature reference P. K. Dutta and M. Puri, J. Phys. Chem. 1989,93, 376-381 (4) discloses a lithium-aluminum mixed hydroxide having alayer structure and containing intercalated benzoate anions.

K. Chibwe and W. Jones in the literature reference J. Chem. Soc., Chem.Commun. 1989, 926-927 (5) describe synthetic hydrotalcite containingintercalated sodium dodecyl sulfate and p-toluenesulfonic acid.

The literature reference K. Chibwe, J. B. Valim and W. Jones, Prep. Am.Chem. Soc. 34 (1989) 507-510 (6) discloses magnesium-aluminum mixedhydroxides having a layer structure and containing intercalatedterephthalic acid, p-toluenesulfonic acid, 2-naphthol-6-sulfonic acid,p- or o-chlorocinnamic acid and n-dodecyl sulfate.

In all three literature references (4) to (6), only the anion-exchangeproperties of these mixed hydroxides are studied.

DE-A 40 02 988 (7) and DE-A 41 06 404 (8) disclose calcium-aluminummixed hydroxides which, inter alia, are modified with phthalic acid,isophthalic acid, terephthalic acid or pyridinecarboxylic acids. Thesecompounds are recommended as stabilizers for halogen-containingthermoplastic resins such as PVC.

The preparation of the mixed hydroxides Ia and IIa of the presentinvention, but also the remaining mixed hydroxides I and II, ie. themodification using the additives (a) to (j), can be advantageouslycarried out in three different ways:

(i) the compounds Ia or IIa are directly synthesized ("in situ") byprecipitation under alkaline conditions from aqueous solutions of M(II)and M(III) salts or aqueous solutions of lithium and aluminum salts inthe presence of the additives (a) to (j);

(ii) the unmodified mixed hydroxides are reacted with the additives (a)to (j) in the presence or absence of a solvent at from 0° to 200° C.;

(iii) the unmodified mixed hydroxides are heated to >200° C., with thetemperature selected being able to be no higher than that which allowsthe mixed hydroxide to subsequently return completely to the originalcrystal structure, the mixed hydroxide thus treated is reacted with theadditives (a) to (j) and is subsequently, if desired, further treatedwith water.

In the case of (ii), the reaction is generally carried out by mixing thecomponents in a suitable apparatus, eg. a stirred reactor, mixer,kneader or a ball mill, preferably at slightly elevated temperature, forinstance from 60° to 200° C. The reaction is usually carried out atpressures of from 0.1 to 50 bar, preferably from 0.5 to 20 bar. If asolvent is to be present, solvents which have been found to be usefulfor this purpose are water, acetone or an alcohol such as methanol,ethanol or isopropanol. The reaction can be followed by furthertreatment with solvent and/or drying.

In the case of (iii), the reaction is generally carried out by mixingthe components in a suitable apparatus, eg. a mixer, kneader or a ballmill at greatly elevated temperature, for instance from 250° to 550° C.The reaction can be followed by further treatment with solvent and/ordrying. The thermal treatment first destroys, at least partially, thestructure of the mixed hydroxide. After the treatment with the additive,the original structure of the mixed hydroxide is regained, particularlywhen further treatment with water takes place.

The mixed hydroxides I and II modified with the additives (a) to (j) arevery useful for the alkoxylation of compounds having active hydrogenatoms. They have the advantage that they have a high selectivity and ahigh reactivity and thus the reaction and cycle times in thealkoxylation are very short. In addition, the by-product spectrum isvery small, in particular low polyalkylene glycol contents are obtained.The alkoxylation products produced thus have a very narrow homologuedistribution. Such alcohol alkoxylates, particularly alcoholethoxylates, have advantages in use compared with the products having abroader distribution, usually prepared using NaOH, KOH or sodiummethoxide. Thus, they have, for example, lower pour points, lowersurface tension, better water solubility and, as a result of a loweringof the free alcohol content (unalkoxylated starting compound), a betterodor. The advantage of a narrower homologue distribution is also clearlyapparent in comparison with the mixed hydroxides which are modified withaliphatic mono- or dicarboxylic acids and are known from the prior art.

The modified mixed hydroxides I and II have the advantage in thealkoxylation reaction that they are more readily dispersible in thereaction medium, eg. long-chain fatty alcohols, but after the reactioncan be easily removed again by filtration. If they do not interfere withfurther use of the products, the mixed hydroxides can remain in theproduct where they can effect an alteration of its rheologicalproperties.

After the alkoxylation is complete, the modified mixed hydroxides I andII can in principle be reused after they have been separated from thereaction mixture in an appropriate manner.

EXAMPLES

Preparation of Mixed Hydroxides Modified with Additives

The modified mixed hydroxides shown in Table 1 as Examples 1 to 13 andComparative Examples 14 and 15 were prepared according to one of thepreparative procedures A to E.

                  TABLE 1                                                         ______________________________________                                                                      Amount of                                       Ex.                           additive                                                                             Preparative                              No.  Mixed hydroxide                                                                            Additive     g!    procedure                                ______________________________________                                        1    Hydrotalcite Benzoic acid                                                                              150    A                                        2    Hydrotalcite p-tert.-Butyl-                                                                            200    A                                                          benzoic acid                                                3    Hydrotalcite Benzoic acid                                                                               80    B                                        4    Hydrotalcite Benzoic acid                                                                               40    B                                        5    Hydrotalcite Benzoic acid                                                                               20    B                                        6    Hydrotalcite p-tert.-Butyl-                                                                            100    B                                                          benzoic acid                                                7    Zinc-aluminum                                                                              Benzoic acid                                                                               80    B                                             mixed hydroxide                                                          8    Hydrotalcite Phthalic     75    C                                                          anhydride                                                   9    Hydrotalcite Benzoic acid                                                                               80    C                                        10   Hydrotalcite Benzoic acid                                                                              150    D                                        11   Hydrotalcite p-tert.-Butyl-                                                                            200    D                                                          benzoic acid                                                12   Hydrotalcite p-Methylbenzoic                                                                           200    D                                                          acid                                                        13   Calcium-aluminum                                                                           Phthalic acid                                                                              33    E                                             mixed hydroxide                                                          for comparison:                                                               14   Hydrotalcite Lauric acid 250    A                                        15   Hydrotalcite Lauric acid 200    D                                        ______________________________________                                    

The hydrotalcite used was a commercial material.

The zinc-aluminum mixed hydroxide of Example 7 was prepared as follows:

A solution of 0.2 mol of aluminum nitrate and 0.7 mol of zinc nitrate in1 liter of water and a solution of 1 mol of sodium carbonate in 1 literof water were added simultaneously at 80° C. to 500 ml of 2 molar sodiumnitrate solution while stirring. The two solutions were run in over aperiod of 60 minutes and the feed was metered in such a way that themixture always had a pH of 6.5. After the precipitation was complete,tile mixture was stirred for a further 30 minutes at 80° C., with the pHagain being kept constant. The precipitate was filtered off, washed freeof nitrate and dried at 100° C. Elemental analysis indicated thefollowing approximate chemical composition of the zinc-aluminum mixedhydroxide: Zn₆ Al₂ (OH)₁₆ !CO₃ ·mH₂ O.

Preparative Procedure A:

300 g of mixed hydroxide together with a saturated solution of theadditive in isopropanol were placed in a stirred vessel. The mixture wasrefluxed while stirring for two hours. The solid phase was subsequentlyfiltered off, washed with pure isopropanol and dried at 110° C.

Preparative Procedure B:

150 g of mixed hydroxide together with the additive were placed in akneader. The mixture was kneaded for two hours at 80° C.

Preparative Procedure C:

150 g of mixed hydroxide together with the additive and 100 g ofdodecanol as solvent were placed in a kneader. The mixture was kneadedfor two hours at 80° C.

Preparative Procedure D:

300 g of mixed hydroxide were heated for two hours at 500° C. andsubsequently placed in a stirred vessel together with a saturatedsolution of the additive in water. The mixture was heated at 80° C. fortwo hours while stirring. The solid was subsequently filtered off,washed with pure water and dried at 110° C.

Preparative Procedure E:

22 g of calcium hydroxide together with 8 g of sodium hydroxide and 16 gof aluminum hydroxide were suspended in 500 ml of water and heated to80° C. A solution of 33 g of phthalic acid in 400 ml of water wassubsequently added at this temperature while stirring. The suspensionwas stirred for a further 2 hours at 80° C. The solid was filtered off,washed with water and dried at 110° C.

In addition, the following modified mixed hydroxides of the presentinvention were prepared from commercial hydrotalcite:

Example 16

(hydrotalcite+benzoic acid)

10 g of dried hydrotalcite together with 4 g of benzoic acid were heatedto 150° C. in an autoclave while stirring. The pressure rose by about 5bar. The autoclave was vented and the mixture was treated at 150° C. fora further four hours. The product was subsequently treated at 200° C.for one hour in a drying oven.

Example 17

(hydrotalcite+n-decanol)

10 g of dried hydrotalcite were dispersed in 200 g of n-decanol at 60°C. for 30 minutes by means of a high-speed mixer. The solid wassubsequently filtered off.

Example 18

(hydrotalcite+benzoic acid)

900 g of dried hydrotalcite together with 90 g of benzoic acid weretreated at 80° C. for four hours in a 5 liter ploughshare mixer runningat 140 rpm. The product was subsequently treated at 150° C. for one hourin a drying oven.

Ethoxylations Using the Modified Mixed Hydroxides

General procedure for the ethoxylation:

1 mol of dodecanol (186 g) and 0.5% by weight of catalyst from Examples11 to 12 or Comparative Examples 14 or 15 were placed in a steelautoclave and dewatered at 120° C. for 1 hour under reduced pressure.The temperature was subsequently raised to 170° C. and 5 mol of ethyleneoxide (220 g) were injected at this temperature, the ethylene oxide feedbeing regulated in such a way that the internal pressure in theautoclave did not rise above 6 bar. After the feeding in of ethyleneoxide was complete, the mixture was stirred further at 170° C. until thepressure was constant. The product obtained was filtered hot.

Table 2 gives the reaction times, polyethylene glycol contents (based onPEG 400), residual alcohol contents and homologue distributions. Thelatter were determined by means of gas chromatography and are given inpercent by area.

It can be seen from the examples that, in comparison with the prior art(Comparative Examples 14 and 15), an improvement was achieved in respectof polyethylene glycol content and the maximum in the homologuedistribution. The residual alcohol contents are in many cases lower thanin the comparative examples.

                                      TABLE 2                                     __________________________________________________________________________                     Residual                                                               Polyethylene                                                                         alcohol                                                      Ex.                                                                              Reaction time                                                                        glycol content                                                                       content                                                                            Homologue distribution  % by area!                      No.                                                                               h!     % by wt.!                                                                            % by wt.!                                                                         E.sub.1                                                                         E.sub.2                                                                         E.sub.3                                                                          E.sub.4                                                                          E.sub.5                                                                          E.sub.6                                                                          E.sub.7                                                                          E.sub.8                                                                         E.sub.9                                                                         E.sub.10                                                                        E.sub.11                       __________________________________________________________________________    1  2      1.7    0.5  1.1                                                                             2.8                                                                             10.1                                                                             21.2                                                                             29.4                                                                             20.1                                                                             9.0                                                                              4.2                                                                             1.0                                                                             0.6                                                                             0                              2  1.5    1.4    0.4  0.9                                                                             2.3                                                                             9.2                                                                              19.8                                                                             31.3                                                                             21.4                                                                             9.5                                                                              3.8                                                                             0.9                                                                             0.5                                                                             0                              3  2      1.9    0.5  1.2                                                                             2.8                                                                             10.2                                                                             21.5                                                                             29.0                                                                             20.2                                                                             9.2                                                                              4.2                                                                             1.1                                                                             0.6                                                                             0                              4  2      2.0    0.7  1.3                                                                             2.7                                                                             10.0                                                                             21.7                                                                             29.5                                                                             19.9                                                                             8.8                                                                              3.5                                                                             1.5                                                                             0.4                                                                             0                              5  2.25   2.0    0.8  1.2                                                                             2.6                                                                             11.0                                                                             20.9                                                                             29.3                                                                             19.5                                                                             9.0                                                                              3.6                                                                             1.7                                                                             0.4                                                                             0                              6  2      1.8    0.3  0.7                                                                             2.2                                                                             9.0                                                                              21.2                                                                             31.9                                                                             20.8                                                                             8.9                                                                              3.5                                                                             0.8                                                                             0.2                                                                             0                              7  2      1.5    0.6  1.2                                                                             3.0                                                                             9.9                                                                              20.9                                                                             29.0                                                                             20.4                                                                             9.1                                                                              4.2                                                                             1.1                                                                             0.5                                                                             0                              8  3.5    1.5    0.5  0.8                                                                             2.0                                                                             10.0                                                                             19.9                                                                             29.9                                                                             22.4                                                                             9.5                                                                              3.5                                                                             1.0                                                                             0.5                                                                             0                              9  1      1.0    0.5  1.1                                                                             2.9                                                                             10.2                                                                             21.7                                                                             29.0                                                                             20.0                                                                             9.0                                                                              4.0                                                                             1.0                                                                             0.6                                                                             0                              10 1.5    1.1    0.5  1.2                                                                             3.8                                                                             12.0                                                                             20.0                                                                             26.5                                                                             18.5                                                                             9.5                                                                              4.7                                                                             2.0                                                                             1.0                                                                             0.3                            11 1      0.8    0.3  1.0                                                                             2.9                                                                             10.0                                                                             20.5                                                                             30.1                                                                             20.9                                                                             9.3                                                                              4.0                                                                             1.0                                                                             0.3                                                                             0                              12 1      1.1    0.3  1.1                                                                             2.8                                                                             10.4                                                                             20.9                                                                             28.0                                                                             18.7                                                                             10.0                                                                             5.0                                                                             1.9                                                                             0.6                                                                             0.1                            for comparison:                                                               14 2.5    2.2    0.7  1.7                                                                             3.9                                                                             12.2                                                                             23.0                                                                             2.50                                                                             20.1                                                                             7.5                                                                              3.8                                                                             1.3                                                                             0.6                                                                             0.2                            15 1.5    1.7    0.5  1.7                                                                             5.3                                                                             13.0                                                                             21.3                                                                             26.0                                                                             19.0                                                                             7.5                                                                              3.0                                                                             1.2                                                                             0.4                                                                             0.1                            __________________________________________________________________________

We claim:
 1. A process for preparing an alkoxylation product comprisingreacting a compound having active hydrogen atoms with at least one of C₂-C₄ -alkylene oxides in the presence of a mixed hydroxide built up ofpolycations and modified with one or more additives and having thegeneral formula I or II

     M(II).sub.1-x M(III).sub.x (OH).sub.2 !A.sub.x/n ·m L(I)

     LiAl.sub.2 (OH).sub.6 !A.sub.1/n ·m L            (II)

where M(II) is at least one divalent metal ion, M(III) is at least onetrivalent metal ion, A is at least one inorganic anion and L is anorganic solvent or water, n is the valence of the inorganic anion A orin the case of a plurality of anions A is their mean valence and x canassume a value of from 0.1 to 0.5 and m can assume a value of from 0 to10, as alkoxylation catalyst, wherein said one or more additives is atleast one selected from the group consisting of(a) aromatic orheteroaromatic mono-or polycarboxylic acids or their salts, (b)aliphatic monocarboxylic acids or their salts from the group phenyl-C₂-C₄ -alkanoic acids, cyclopentanecarboxylic acid, cyclohexanecarboxylicacid, cyclohexyl-C₂ -C₄ -alkanoic acids, cinnamic acid, o- orp-chlorocinnamic acid and pyridylacetic acids, (c) monoesters ofdicarboxylic acids or their salts, (d) carboxylic anhydrides, (e)aliphatic or aromatic sulfonic acids or their salts, (f) C₈ -C₁₈ -alkylsulfates, (g) C₈ -C₅₀ -n-alkanes, (h) polyetherols or polyether polyols,and (j) alcohols or phenols,which are not build in between the layers ofthe mixed hydroxide I or II.
 2. A process for preparing alkoxylationproducts as claimed in claim 1 in the presence of a mixed hydroxide ofthe general formula I in which M(II) is magnesium, M(III) is aluminumand A is carbonate.
 3. A process for preparing alkoxylation products asclaimed in claim 1, wherein the mixed hydroxide I or II contains asadditives benzenemonocarboxylic or benzenedicarboxylic acids, in whichthe benzene ring can be additionally substituted by from one to three C₁-C₄ -alkyl groups, phenyl-C₂ -C₄ -alkanoic acids, cyclohexanecarboxylicacid, cyclohexyl-C₂ -C₄ -alkanoic acids, C₁ -C₁₈ -alkylmonoesters ofphthalic acid, hexahydrophthalic acid, maleic acid or terephthalic acid,maleic anhydride, phthalic anhydride, hexahydrophthalic anhydride,benzenesulfonic acid, p-toluenesulfonic acid, p-dodecylbenzenesulfonicacid, alkali metal dodecyl sulfates, n-dodecane, n-alkanols having from9 to 18 carbon atoms or salts of the acids specified.
 4. A process forpreparing alkoxylation products as claimed in claim 1, wherein theadditives (a) to (j) are used in a molar ratio to the mixed hydroxides Ior II of from 0.01:1 to 10:1.
 5. A process for preparing alkoxylationproducts as claimed in claim 1 by reaction of C₁ -C₃₀ -alkanols or C₃-C₃₀ -alkenols as compounds having active hydrogen atoms.
 6. A processfor preparing alkoxylation products as claimed in claim 1, wherein themixed hydroxides I or II are used in amounts of from 0.1 to 5% byweight, based on the weight of the compounds having active hydrogenatoms.
 7. A process for preparing alkoxylation products as claimed inclaim 1, wherein the reaction is carried out at from 80° to 230° C. andpressures of from 2 to 10 bar.
 8. A mixed hydroxide built up ofpolycations and having the general formula Ia or IIa

     M(II).sub.1-x M(III).sub.x (OH).sub.2 !A.sub.x/n ·m L(Ia)

     LiAl.sub.2 (OH).sub.6 !A.sub.1/n ·m L            (IIa)

where M(II) is at least one divalent metal ion, M(III) is at least onetrivalent metal ion, A is a least one inorganic anion and L is anorganic solvent or water, n is the valence of the inorganic anion A orin the case of a plurality of anions A is their mean valence and x canassume a value of from 0.1 to 0.5 and m can assume a value of from 0 to10, which has been modified with at least one additive selected from thegroup consisting of(a) aromatic or heteroaromatic mono-or polycarboxylicacids or their salts, (b) aliphatic monocarboxylic acids or their saltsfrom the group phenyl-C₂ -C₄ -alkanoic acids, cyclopentanecarboxylicacid, cyclohexanecarboxylic acid, cyclohexyl-C₂ -C₄ -alkanoic acids,cinnamic acid, o- or p-chlorocinnamic acid and pyridylacetic acids, (c)monoesters of dicarboxylic acids or their salts, (d) maleic anhydride,phthalic anhydride or hexahydrophthalic anhydride, (e) aliphaticsulfonic acids or their salts, (f) C₈ -C₁₈ -alkyl sulfates, (g) C₈ -C₅₀-n-alkanes, and (j) alcohols or phenols, which are not built in betweenthe layers of the mixed hydroxide I or II, with the exception of benzoicacid and its salts in the case of a lithium-aluminum mixed hydroxidehaving a layer structure, with the exception of terephthalic acid, p-and o-chlorocinnamic acid and the corresponding salts and of n-dodecylsulfate in the case of magnesium-aluminum mixed hydroxides having alayer structure, and also with the exception of phthalic acid,isophthalic acid, terephthalic acid and pyridinedicarboxylic acids inthe case of calcium-aluminum mixed hydroxides.
 9. A process forpreparing a mixed hydroxide Ia or IIa as claimed in claim 8, whichcomprises precipitating the compounds Ia or IIa under alkalineconditions from aqueous solutions of M(II) and M(III) salts or aqueoussolutions of lithium and aluminum salts in the presence of said at leastone additive.
 10. A process for preparing a mixed hydroxide Ia or IIa asclaimed in claim 8, which comprises reacting the unmodified mixedhydroxide with said at least one additive in the presence or absence ofa solvent at from 0° to 200° C.
 11. A process for preparing a mixedhydroxide Ia and or IIa as claimed in claim 8, which comprises heatingthe unmodified mixed hydroxide to >200° C., with the temperatureselected being able to be no higher than that which allows the mixedhydroxide to subsequently return completely to the original crystalstructure, reacting the mixed hydroxide thus treated with said at leastone additive and subsequently, if desired, further treating it withwater.